The Cookiecutter shark, Isistius brasiliensis, also known as the cigar shark or luminous shark, is a small rarely-seen dogfish shark.
Anatomy and morphology
The Cookiecutter sharks often glow green and grow up to 20 in (50 cm) long. The underside of the shark is bioluminescent, glowing a pale blue-green that matches the background light from the ocean's surface that serves as camouflage...